The ceremony to open the symbolic white tap of the gas pipeline in the town of Lubmin in northern Germany was also attended by Dutch Prime Minister Mark Rutte and French Prime Minister Francois Fillon.

"This is a long-awaited event which signifies the strengthening of relations between Russia and the European Union. This event will enhance the security regime, including energy security in Europe," President Medvedev said at a news conference.

Russian natural gas and the electricity produced with it will "make the life of a large number of people more comfortable," Medvedev said, adding he he hoped the European economy and gas demand would grow.

'We expect that the economy of the European Union will be able to overcome all current difficulties and attain steady growth, after which annual additional requirements of our European partners for gas may increase to quite high levels by 2020 - to 200 billion cubic meters, according to expert estimates," he said.

Natural gas transportation via the first stage of the Nord Stream pipeline will reach its full capacity of 27.5 billion cu m as soon as 2012, Gazprom Deputy CEO Alexander Medvedev said.

"In 2012, the first stage of Nord Stream will transport up to 27.5 billion cu m. Specific volumes will depend on customers' requests but the contractual volume for 2012 is 27.5 billion cu m," he said.

The pipeline will deliver Russian gas via the Baltic Sea to Germany, bypassing key transit countries Ukraine and Belarus. Gazprom's Medvedev said the company would not cut gas transit via Belarus after the launch of Nord Stream.

Russia currently provides almost 30 percent of the gas consumed in Europe.

The $11-billion Nord Stream project includes two roughly parallel pipelines with an overall annual capacity of 55 billion cubic meters.

Russia's gas giant Gazprom, which holds 51 percent in Nord Stream, has already signed long-term gas contracts via the Nord Stream pipeline with several European countries, including Germany, Denmark, the Netherlands, Belgium, France and Britain.